Struggling Republican White House hopeful Mitt Romney clashed repeatedly with his surging rival Rick Santorum on Wednesday, in a crucial TV debate as the pair battle for frontrunner status.
In the last televised debate before two key polls next week -- and before so-called "Super Tuesday" on March 6 -- the two men locked horns notably on fiscal issues, religion and immigration.
"You're misrepresenting the facts. You don't know what you're talking about," Santorum told Romney bluntly during the two-hour debate in Arizona, one of two states holding Republican primaries next Tuesday.
Romney, who is battling to retain his frontrunner status against the Christian conservative, lambasted Santorum's voting record during his time as a US senator from Pennsylvania.
"During his term in the senate, spending grew by some 80 percent in the federal budget," Romney said, referring to "a whole series of votes. Voting to fund planned parenthood, expand the department of education."
On religion, Santorum jabbed his finger repeatedly as he accused Romney of facilitating access to insurance-funded contraception when he was governor of Massachusetts -- but the former investment fund boss turned the tables.
"Don't look at me, take a look in the mirror," Romney told Santorum, seated next to him, questioning his voting record on birth control -- in theory defined by his Catholic faith -- in the Senate.
Santorum soared from a distant third into pole position after a trio of wins earlier this month in the state-by-state voting contest to decide who takes on Democratic President Barack Obama in November's general election.
Romney, who seemed to have a lock on the Republican nomination after trouncing his rivals in Florida and Nevada, is desperate to stop the rot and has launched a major advertising blitz before next week's votes.
Up for grabs on February 28 are Michigan, where Romney was born and his father was governor, and Arizona, another supposed Romney stronghold where a significant proportion of the electorate shares his Mormon faith.
Both states were considered shoo-ins for Romney until a short time ago, but such has been the extent of Santorum's popular surge that the Christian conservative now has a chance of taking both.
A Santorum win in either would be a huge blow to Romney going into "Super Tuesday" on March 6, when 10 states vote simultaneously in a potentially decisive night for the Republican race.
A Quinnipiac University poll out Wednesday found Santorum leading Romney 35-26 percent among nationwide Republicans, followed by former House speaker Newt Gingrich at 14 percent and Texas congressman Ron Paul at 11 percent.
But the poll found that Obama would defeat Santorum in a general election while an Obama-Romney face-off would be too close to call, adding fuel to Republican concerns about Santorum's electability in a general election.
"If he were to lose Michigan, the story will be that he can't even win the state where he was born and grew up and where his father was governor," said Peter Brown, assistant director of the Quinnipiac University Polling Institute.
"On the other hand, if he wins Michigan, he is the comeback kid," he told AFP.
The Republican establishment fears Santorum, a fierce opponent of gay marriage and abortion, could be a liability in a head-to-head contest with Obama as his moralizing could turn off independent voters.
Romney, employing the same tactic he used to good effect in Iowa and Florida to see off strong challenges from Gingrich, has launched a barrage of vitriolic attack ads against his chief opponent.
Romney received a boost hours before the debate, when he was endorsed by Michigan's second largest paper, The Detroit News.
In Arizona, more than 200,000 people had already cast ballots before the debate, officials said Wednesday. "I would say turnout is good," Evonne Reed, spokeswoman for the Maricopa County Recorder's office, told CNN.
Romney's strong debates in Florida were important in his turnaround in fortunes there, while Gingrich's stellar performances in South Carolina saw the former House speaker briefly surge ahead in the topsy-turvy race.
Among the questions posed at Wednesday's debate, one was dealt with swiftly: the four candidates were asked to sum themselves up in one word.
Paul said "consistent," followed by Santorum with "courage." Romney, who has been the steadiest in the polls while rivals have surged into the lead only to collapse quickly, chose "resolute."
Gingrich, who was the frontrunner of choice before Santorum, chose "cheerful," drawing a warm reaction from the audience.